Field of the Invention
The present invention relates to a versatile multi-layer elastomer or thermoplastic elastomer based thermal and/or sound insulation material with improved fire retardant properties together with low smoke generation, the process for manufacturing of such material and the use of such material and resulting composites.
Description of the Background Art
Elastomeric materials have been used since long time for insulation purposes as expanded material (see e.g. brands Armaflex®, K-Flex®). However, as elastomers are of organic nature and due to the fact that cellular material is more sensitive to ignition than massive elastomer, said expanded elastomers tend to be flammable to very flammable.
Numerous attempts have been taken to improve the flame retardancy of organic polymer foams, such as by loading the elastomer compound with internal flame retardants as it is standard in the rubber industry and/or by applying flame retardant protective layers: one could think of composites where specially flame-protected polymers form the outer layer, but the most widespread approach for fire protection is the use of an outer layer consisting of a metal foil or sheet, mostly aluminium due to applicability and cost issues, often together with one or more inner layer(s) showing no or low combustibility.
This technology has been used to almost an exhaust in many varieties: aluminium honeycombs filled with rigid foam, metal foil with mineral wool underneath, foil layer wire netting underneath, outer foil in some varieties, perforated foil, fibres underneath, or foil together with intumescent systems. Most inventors claim the use of metal foil or sheet and fibres (woven or nonwoven) for example in conjunction with low-combustible fibres (aluminium/polyester or polyamide or several fibrous layers), but mostly non-combustible fibres. There are several patents in which the inventors all use metal—mostly aluminium—foil as the outermost layer with (glass) fibre or tissue or scrim underneath and foil with holes, fibres.
Other inventors claim the use of low-combustible fibres or non-combustible fibres (mainly glass fibres) only as an outer layer, sometimes in conjunction with other layers, such as glass fibre coating, fibres in matrix, internal layer low-combustible material, inorganic fibre layer, partially filled with non-combustibles, non-combustible fibre and bamboo layer, fibre on foam-filled honeycombs, fibre reinforced outer resin layer or fibres/foils on intumescent layer. Other patents claim glass fibres as outer layer or the use of multiple fibre layers for building a structure, but they do not target fire performance explicitly. CN 1613640 mentions a double felt layer with flame retardant impregnation; U.S. Pat. No. 5,698,302 mentions a double glass fibre layer on rigid foam wherein however, the layer is neither described nor intended as fire retardant fibrous material, as it is applied on polymeric material comprising flame retardant resin itself; DE 19640887 claims a layer of fibre-reinforced silicate for fire protection purposes.
All of the aforementioned inventions focus on mainly rigid foams to protect, except GB 2378919, where a rubber-like inner layer is disclosed, however, the whole composite has to be essentially rigid again. In total, all these methods indeed cover a large variety of requirements concerning flame retardancy; however, their individual versatility is limited and their performance is strongly depending on the substrate, on how the layers are applied etc. Therefore, most of the aforementioned inventions require or at least mention flame retardant properties for the substrate itself, too.
Requirements and flammability test related approvals within the building industry become more and more global, but also more precise and application-related and therefore more challenging (e.g. ASTM E-84, EN 13823), as smoke creation and density are considered in addition to the flammability.
Accordingly, we found during our research that the aforementioned prior art is not suitable to safely reach the highest possible flame retardancy classes for organics (e.g. B s1 d0 for EN 13823/EN 13501-1, V-0 for UL 94 etc.) even for the most widespread polymer foam bases, and in some cases these systems even lead to worse performance (see results for laminated AF in Table 1). Systems that perform better (e.g. at least reaching B s3 d0 or V-1 class, respectively) showed to be expensive, complex and neither economic nor ecologic.
A general deficiency of the aforementioned materials is the fact that the flame retardant measures taken will lead to incomplete combustion, thus particles being content of the smoke leading to high smoke density, together with partially high smoke creation, too. There are other reasons for the fail of the traditional protection systems that are discussed below.
Some prior art is not based on traditional systems: KR 1020060021127 reveals composites with a protective polymer layer on an aluminium foil layer which itself is on top of foam. However, this system is not claimed for fire protection performance, and possibly would not match the respective requirements as the polymer is too easy burning. CH 650196 is describing an interesting composite said to be flame-retardant where the aluminium foil is perforated and being the second layer, covered by an outer layer of polyester fibres containing flame-retardants. Also the aforementioned JP 8199709 is describing a system where the metal foil does not necessarily have to be the outermost layer.
However, even these non-classic systems show deficiencies concerning applicability, reproducibility and consistency of the fire test results according to our research. For example, JP 8199709 correctly describes that the slow-burning outer layer containing flame retardant agents will disperse the heat of the burn by aid of the aluminium conductor beneath, however, we found that from a certain point of time on this dispersion ability is saturated and the overheating of the metal layer will cause an undesired flashover of both the outer layer and the substrate, leading to complete combustion of the composite around the foil. The composite mentioned in CH 650196 will show this effect at a slightly later point of time, but will end in a flashover anyway. The reason for the retarding of the flashover here is due to the perforation of the foil allowing the heat to disperse even into the substrate, but not up to a critical level where flammable gases would be formed. Eventually, also the correct assumption of GB 2222185 that a first layer that can melt away from flames would be of protective function showed to be of no use when applied for aforementioned testing methods and approvals as the melt layer finally ignited spontaneously anyway.
Additionally we observed significant creation of dark and/or dense smoke before and after the flashover in all three cases which would be another negative criterion concerning approvals. Furthermore, the vast majority of aforementioned layered materials would be very stiff and thus destroy some advantages provided by elastomeric, thus flexible expanded materials, such as for good and easy mounting and sealing tolerances etc.